1. Field of the Invention
The present invention relates to information storage, and more particularly relates to a technology preventing the steal of information.
2. Description of the Related Art
As a technology for preventing data stored in a semiconductor device, such as memory or the like, from being illegally read by a third party, a variety of technologies have been traditionally proposed.
For example, Japanese Patent Application No. H5-88986 discloses a technology for destroying information stored in information storage means of a capsule when the electric field of a piezoelectric material forming the capsule changes.
Japanese Patent Application Nos. 2001-195307 and H11-328036 discloses a technology for erasing information stored in non-volatile memory when voltage drop due to removing a thin film battery in order to observe an IC chip is detected.
Japanese Patent Application No. H10-320293 discloses a technology for providing a sensor for detecting the opening of an IC card and erasing the data of non-volatile memory in an IC card when the opening is detected.
Japanese Patent Application No. H9-16477 discloses a technology for removing the backup of the secondary storage device storing a decoding key to erase the decoding key when the primary storage device storing secrete data is disconnected from a bus line.
Japanese Patent Application No. 2002-73422 discloses a technology for breaking down data to be stored into a plurality of data pieces, any one of which has no meaning, storing each of them in different memory and erasing data stored in memory other than the removed one when the illegal removal of data in any of them is detected.
Japanese Patent Application No. 2001-202167 discloses a technology for encoding memory contents in a computer when there is an instruction to switch its computer power off or an instruction to enter a power-saving operation state, and for decoding the memory contents in the computer when there is an instruction to switch the computer power on or to return to a normal operation state.
Since some of the above-described technologies erase data against an illegal reading operation, even a regular user cannot regain the lost data after the illegal reading.
Since some of the above-described technologies use an encryption technology, the encoding/decoding gives a heavy process load to a system. Therefore, it is not easy for a system without any allowance in a processing capacity to adopt them.